When Napoleon joins his army in March 1796, he finds himself in command of 37,000 men who are demoralized, badly fed and unpaid. During April he leads them in a series of rapid victories which vastly raise the soldiers' spirits and hold out the promise of rich loot under this energetic young commander.

The allies facing Napoleon are the Austrians, committed to defending their extensive territory around Milan - and the Sardinians whose realm extends from Savoy and Nice west of the Alps to Piedmont, with its capital at Turin, on the Italian side. (They are called Sardinians because the duke of Savoy is also the king of Sardinia, a senior title.)

Napoleon's strategy is to divide and to surprise his enemies. Instead of taking the obvious route along the coast, he leads his army through Alpine passes to catch the Austrians unaware at Montenotte on April 12. It is the first of a rush of victories against Austrians and Sardinians separately. The allies are successfully prevented from joining forces against their fast-moving opponent.

At the end of the month Napoleon issues a proclamation to his men, using a certain degree of hyperbole to trumpet their achievements: 'Soldiers! In fifteen days you have gained six victories, taken twenty-one colours and fifty-five pieces of artillery, seized several fortresses and conquered the richest parts of Piedmont.'

By April 28, in the armistice of Cherasco, the king of Sardinia is ready to make peace with France and to cede his territories of Savoy and Nice - both in practice already occupied, since 1792, by French republican forces.

Napoleon's conquest of Piedmont is repeated, in similar piecemeal fashion, in other regions of Italy. He defeats the Austrians at Lodi on April 10 and enters Milan five days later. Subsequent campaigns lead rapidly to armistices with the dukes of Parma (May 9) and Modena (May 17) and with the pope, Pius VI, on June 23. Ancient and enfeebled Venice is unable to offer any opposition to the conqueror. In May 1797 Napoleon deposes the last of the doges and sets up a provisional democracy.

In all these subdued territories Napoleon has been energetically imposing the new French ways, often with the enthusiastic support of locals as impatient as the French with the remnants of feudalism. Northern and central Italy is reorganized as the Cisalpine Republic, while the territory of Genoa becomes the Ligurian Republic.

During the winter of 1796-7 there are prolonged and complicated engagements between French and Austrian forces round Mantua, but by April Napoleon is secure enough to move northwards against Vienna itself. He is just two days' march away from the city, at Leoben, when the Austrian emperor agrees an armistice.

By the terms of the peace, signed at Campo Formio in October, Austria cedes to France the Austrian Netherlands and all her territory in northern Italy. In return, as a sop, Napoleon gives the emperor Venice.

All this is negotiated by the young general on his own initiative. The Directory, busy with the coup d'état of Fructidor, is in no position to control him in his triumph. Moreover, like Napoleon's troops, the government can hardly be indifferent to the material result of his success. A steady stream of booty, both of money and art, makes its way back to France (including, looted once again, the famous bronze horses from St Mark's in Venice). Exported French republicanism may be a blessing, but it does not come cheap.

Napoleonic Italy: 1800-1814

During 1799 Austrian and Russian armies of the Second Coalition recover Italy as rapidly and as conclusively as Napoleon (now far away in Syria) won it two years previously. But with Napoleon's return to France later in that year, and his achievement of power as first consul, the region becomes again one of his priorities.

Napoleon's victory at Marengo, in June 1800, is the start of the French recovery of Italy. The process is completed in stages up to 1809, by which time every part of the peninsula is under French control.

The whole of the north Italian plain from Milan to Venice, together with the Po valley and the Adriatic coast down to below Ancona, becomes the kingdom of Italy within Napoleon's French empire. The king is Napoleon himself, crowned with the iron crown of Lombardy in full medieval pomp in Milan cathedral in May 1805. His viceroy in the kingdom is his stepson, Eugène de Beauharnais.

The kingdom of Italy marches on the Adriatic coast with the kingdom of Naples, comprising the whole of southern Italy and ruled from 1808 by Joachim Murat, the husband of Napoleon's sister Caroline. (Ferdinand, the legitimate king of Naples, has withdrawn to Sicily - where he survives under British protection.)

The rest of mainland Italy, consisting of three regions, is by now directly annexed to the French empire. One region is Liguria, the coastal area around Genoa. Another is Tuscany, where in 1809 Napoleon makes his sister Élisa the grand duchess. And the third is the papal states, together with the holy city of Rome itself.

The holy see is the last and the most controversial piece of the French-Italian jigsaw to be set in place.

The French and Rome: 1793-1814

The papacy is ill-equipped to cope with either French revolutionary zeal or Napoleonic empire building. The years of French ascendancy are a long tale of disaster for Rome.

An incident of 1793 sets the tone. A French diplomat in Rome, Nicolas de Basseville, indulges in a provocative display of the tricolour, symbol of French anti-clerical republicanism. A Roman crowd attacks him and he dies the next day. Four years later, when Napoleon reaches as far south as Ancona in an advance on Rome, this incident remains a specific grievance for which France holds the pope responsible - demanding and receiving 300,000 livres as compensation for Basseville's family.

The pope who has to negotiate with Napoleon in 1797 is Pius VI. The price of persuading the French intruder to head north again, agreed in the peace of Tolentino, is a massive indemnity, the removal of many works of art from the Vatican collections and the surrender to France of Bologna, Ferrara and the Romagna.

This reduction of the papal states is only the beginning of Pius's troubles. In the last few days of 1797 a disturbance outside the French embassy in Rome results in the death of a French general. This is made the pretext for a French army to occupy Rome and to seize the pope, who is taken off to captivity in France - where he dies in 1799.

The new pope, Pius VII, is at first conciliatory towards Napoleon. He agrees the concordat of 1801. He travels to Paris in 1804 to officiate at Napoleon's imperial coronation. But by 1808 relations have deteriorated. The pope annoys Napoleon by refusing to sanction the annulment of his brother Jerome's marriage and, perhaps more significantly, by not bringing the ports of the papal states into the Continental System.

The result is that a French army occupies Rome in February 1808. In the following month another section of the papal states (the Marches) is annexed to the Napoleonic kingdom of Italy.

Napoleon follows up these affronts by annexing in 1809 all that remains of the papal states, including the city of Rome, and by announcing that the pope no longer has any form of temporal authority. Pius VII responds by an immediate use of his spiritual authority, excommunicating Napoleon himself and everyone else connected with this outrage. He is immediately arrested and removed to imprisonment in France.

These are the events which bring the entire Italian peninsula under French control by 1809. The situation remains unchanged until after Napoleon's defeat at Leipzig in 1813 - an event followed by Austrian recovery of much of Italy and a subsequent seal of approval at the congress of Vienna.

Austria and Italy: 1815-1831

The terms agreed at the congress of Vienna return Italy almost precisely to the situation prevailing before the French intrusion. The king of Sardinia (head of the ancient house of Savoy) recovers his bloc of territory around the western Alps, comprising Savoy, Nice and Piedmont; he acquires also a valuable extension along the coast in the form of Liguria, which previously was the republic of Genoa.

Austrian rule is restored in the large and rich area of northern Italy - from Lombardy, through Parma and down into Tuscany. Here too there is an important addition resulting from the Napoleonic upheavals. Venetia, the province of the republic of Venice, is added to the Austrian empire.

In the central part of the peninsula Rome recovers the papal states. And the whole of southern Italy, previously consisting of the two kingdoms of Naples and Sicily, reverts to its Bourbon monarch Ferdinand. His realm is now merged into a single kingdom of the Two Sicilies, of which he becomes Ferdinand I (having previously been Ferdinand IV of Naples and Ferdinand III of Sicily).

Among these Italian powers Austria is by far the strongest. With Metternich's determination to preserve the royalist status quo in Europe, Austrian armies become the natural policemen on patrol in Italy for any sign of revolution. And there seems to be much going on of a suspicious nature.

In the Italy of the restoration there are many secret societies harbouring radical ideas. Army officers and civil servants, who in many cases have had first-hand experience of the modern French style of administration, are disturbed to find themselves in a reimposed version of the ancien régime.

They crave independence from reactionary rulers. And some are influenced by a vision deriving from Napoleon's hold on the entire peninsula - that of a united Italy, under a single government.

The earliest and best-known among Italy's revolutionary groups are the Carbonari, meaning 'charcoal-burners'. As befits a secret society, their origin is uncertain. When they first emerge from the shadows, in around 1806, the Carbonari are anti-French, opposing in particular the royalist aspect of French rule now that Napoleon is emperor.

After 1815 their quarrel is with the restored royal dynasties in Italy. The first real success of the Carbonari is a revolution in Naples in 1820. It causes Ferdinand to bring in a liberal constitution. But nine months later he invites an Austrian army into his kingdom and returns to absolutist rule.

This pattern of Austrian involvement is soon repeated elsewhere. Secret societies achieve a revolution in Piedmont in 1821, leading to the abdication of the king and a brief spell of constitutional rule - until an Austrian army marches into Turin and restores the status quo. Similarly, when the revolutionary ferment of 1830 results in unrest in the papal states (in February 1831), the papacy regains control with the help of Austrian forces.

These events prompt new policies among Italy's radicals. All are agreed that the Austrians must be removed and Italy united, and it now seems clear that the Carbonari and their like are not up to the task. But how should it be achieved? This is a matter of passionate disagreement.